1. Field of the Invention
This invention generally relates to the manufacturing and construction of optical devices and more specifically to the positioning of lenses spaced along an axis, such as an optical housing.
2. Description of Related Art
In a number of optical devices it is important to position lenses or other optical elements accurately with respect to each other along a device axis. Rigid endoscopes are an example. Rigid endoscopes are elongate optical devices in which a plurality of axially spaced optical elements including lenses relay an image from an objective to an eyepiece along a device axis that is also the optical axis. It is important that the axial spacing between individual optical elements, such as the elements in the relay lens system, be maintained accurately in a wide variety of environmental conditions including widely varying temperature conditions as encountered during autoclaving and conditions of mechanical shock. Furthermore it is often important to maintain all the optical elements in a sealed environment to prevent moisture from accumulating along an optical path in order to maintain image quality.
A number of approaches for providing axial positioning of optical elements have been disclosed in the prior art. Some use a process of deforming certain structures and are disclosed in the following references: GB1556475 (1979) Epworth et al.
1,587,131(1926)Tillyer3,949,482(1976)Ross4,776,670(1988)Kessels et al.5,305,406(1994)Rondeau5,493,452(1996)Hoshino et al.5,810,713(1998)Rondeau et al.5,969,887(1999)Hagimori et al.6,201,649(2001)Rudischhauser et al.6,263,133(2001)Hamm6,398,723(2002)Kehr et al.6,462,895(2002)Hunter6,487,440(2002)Deckert et al.
Generally speaking these methods deform an outer tube in an attempt to position each optical element along an optical axis. In some approaches the resulting structure merely engages the periphery of the lenses and relies on sliding friction to maintain accurate location. However, in many situations shock forces can overcome the sliding friction exerted in such devices so an optical element can be displaced. In others a tube is penetrated to provide a tab that blocks motion of the lens axially. Piercing the outer tube destroys any ability to isolate the optical element from the environment surrounding the optical system, particularly in the case of endoscopes that require autoclaving.
What is needed is an optical device and a method for manufacturing an optical device with positive positioning of individual optical elements without any need to penetrate a supporting structure.